Life cycle ofSphecophaga vesparum(Curtis) (Hymenoptera: Ichneumonidae), a parasitoid of some vespid wasps

Abstract

The literature on the biology of Sphecophaga vesparum (Curtis) is reviewed. New data are added and the life cycle is outlined. Winged adults emerge from yellow, overwintering cocoons from one to four springs/summers after the season in which the cocoons were formed, and may live for up to 3 weeks. The species is at least facultatively deuterotokous, but mating can occur. Within wasp nests, winged and brachypterous females prefer to oviposit into cells within which host pupation has most recently occurred. The species is ectoparasitic on wasp iinmatures within capped cells. Both female morphs lay three kinds of eggs: those that give rise to white cocoons and then brachypterous females within 13 days, those that give rise to weak, yellow cocoons that produce winged females and possibly males within 15 days, and those that give rise to resistant, yellow, overwintering cocoons. Many generations may originate from one invasive winged female in one year.The species is very well adapted to take maximum advantage of its host's life cycle. Productivity of individual females, whether fertilisation occurs, and the mode of entry of winged females into wasp nests, have yet to be determined.

Factors influencing reproductive strategies of the vespid parasitoidSphecophaga vesparum vesparum(Hymenoptera: Ichneumonidae)

“…Schmieder (1939) considered the intermediate stage of cocoon formation (weakwalled yellows; reported by Reichert (1911)) in S. v. vesparum (Curtis) to result from imperfectly specified dimorphism. Donovan (1991) observed that "whites fed from 3-4 days and yellows 4-5 days" supporting the suggestion that differences in the nutritional input to the parasitoid from the host were important in determining the type of cocoon formed.…”

“…They continue to lay eggs within the parental nest, and multiple generations follow during the same season. Donovan (1991) reported that the key to the parasitoid flourishing within a vespid colony appears to be the production of "white" and/or "weak-walled yellow" cocoons, while "yellow" cocoons ensure continuation of the parasitoid population in following seasons.…”

“…has suggested that temperature may also influence the type of cocoon formed, and that low temperatures may inhibit cocoon production altogether. Schmieder (1939) and Donovan (1991) suggested that cocoon type may be determined by an intrinsic genetic factor, so that each female lays only one of three distinct types of egg. If this were the case, eggs laid on identically aged pupae in identical conditions could produce a range of cocoon types.…”

“…Winged male and female Sphecophaga emerge from cocoons in the remains of old wasp nests in spring, one to four seasons after their cocoons were formed (Donovan 1991).…”

No evidence for establishment of the wasp parasitoid,Sphecophaga vesparum burra(Cresson) (Hymenoptera: Ichneumonidae) at two sites in New Zealand

“…The resulting parasitoid larvae feed on the wasp pupae, killing them in a few days. Pupating parasitoid larvae form one of three types of cocoon (Donovan 1991), depending on the nutrition the larva has received (Harris & Rose 1999). Two cocoon types give rise to adults within the same season-thin-walled white cocoons produce brachypterous adults, and thinwalled yellow cocoons produce apterous adults.…”